This invention relates to a piping examination apparatus for the maintenance and inspection of a number of closely clustered pipes. More particularly, the invention relates to a swinging-type automatic examination apparatus for automatically examining piping while "walking" across the narrow spaces between pipes.
Nuclear reactors are subjected to periodic examination to verify the safety of the equipment. Since the examination of the primary system of a nuclear reactor is an operation performed in a radioactive environment peculiar to nuclear power plants, reducing the exposure of the examination personnel to radiation and shortening the time required for the examination are important considerations. Accordingly, use is made of a remotely controlled mobile apparatus equipped with sensors.
FIG. 8 is a perspective view illustrating the primary cooling system of an advanced thermal reactor. Numeral 81 denotes a nuclear reactor, 82 a pressure tube assembly, 83 a calandria tank, 84 one of more than 200 inlet pipes, 85 one of more than 200 outlet pipes, 86 a steam drum, 87 a main steam pipe, 88 a descending pipe, 89 a recirculation pump, and 90 a lower header.
The outlet pipes 85 of the reactor 81 have a little less than 3000 welding seams, and the inlet pipes 84 have a little more than 4000 welding seams, for a total of about 7000 welding seams. The outlet pipes 85 constituted by a group of small-diameter pipes are arranged at a pitch of 240 mm.times.150 mm--250 mm at the horizontal portions and at a pitch of 410 mm around the steam drum 86 and at the vertical portions. The inlet pipes 84 are arranged at a pitch of 200 mm.times.120 mm--250 mm at the horizontal portions and at a pitch of 200 mm around the lower header 90 and at the vertical portions. Thus, there is not enough space between the inlet and outlet pipes to allow an examiner to approach and inspect them, and the radiation level surrounding the piping is comparatively high. Accordingly, there is a need to develop a remotely controlled, automatic examination apparatus for the purpose of reducing exposure to radiation, shortening the time required for the examination and enlarging the examination region to include the spaces among the innermost pipes.
In the development of methods and apparatus for examining these inlet and outlet pipes, these pipes were considered to be obstacles to examination. However, a remotely controlled, automatic examination system has been tested and developed which uses the inlet and outlet piping as a foothold for an examination device and is adapted to wander along and across the pipes automatically by being remotely controlled.
FIG. 9 is a view illustrating the overall arrangement of this remotely controlled, automatic examination system for examining outlet pipes, and FIG. 10 is a view illustrating the system in which a mobile unit included in the system "walks" from one outlet pipe to another for examining the same. Numeral 91 denotes a control unit, 92 a data display unit, 93 a remotely controlled mobile unit, 94, 95, 9 pipes , 97, 98 yokes, 99-102 clamping devices, and 103 an arm.
In FIG. 9, the remotely controlled unit 93 is remotely controlled by the control unit 91 and is adapted to slide along piping, walk from one pipe to another in a direction perpendicular to the pipes, and examine a pipe while clamped thereto. Data indicative of the position of the mobile unit 93 of the examination system and the results of examination are displayed by the display unit 92 and stored in memory.
The operation of the remotely controlled mobile unit 93 will now be described with reference to FIG. 9.
The clamping devices 99, 100 are provided on the ends of the yoke 97, and the clamping devices 101, 102 are provided on the ends of the yoke 98, the clamping devices having the same spacing between them as the pipes. The distal ends of the clamping devices 99-102 open and close in response to control signals from the control unit 91 to grasp and release the pipes. The yokes 97, 98 are interconnected by an arm 103. With the point at which one yoke is connected to the arm 103 serving as a center, the other yoke swings about this center so as to describe a semicircle the radius of which is the length of the arm 103.
In the state shown at (A) of FIG. 10, the clamping devices 99, 100 and 101, 102 of the yokes 97 and 98 are situated on the pipes 94, 95 and are clamping these pipes. Next, at (B) of FIG. 10, the clamping devices 99, 100 are opened and the yoke 97 is swung so as to describe a semicircle about the point at which the yoke 98 is connected to the arm 103. The clamping devices 99, 100 then move onto the two mutually adjacent pipes 95, 96 and are closed to clamp these pipes, as shown at (C) of FIG. 10. Next, the clamping devices 101, 102 are opened and the yoke 98 is swung so as to describe a semicircle about the point at which the yoke 97 is connected to the arm 103, as illustrated at (D) of FIG. 10. The clamping devices 101, 102 then move onto the two mutually adjacent pipes 95, 96 and are closed to clamp these pipes, as shown at (E) of FIG. 10. Thereafter, these operations are repeated so that the mobile unit 93 can be moved to any desired piping position.
In the state shown at (A) or (E) of FIG. 10, the clamping devices 99, 100 are opened and a sliding device 104 is driven into operation to advance the yoke 98 a prescribed stroke (10 mm in the test apparatus) axially of the piping and then stop the yoke, after which the clamping devices 99, 100 are closed.
Next, the clamping devices 101, 102 are opened and the sliding device 104 is driven into operation again to advance the yoke 97 the prescribed stroke axially of the piping (in the direction of yoke 98) and then stop the yoke, after which the clamping devices 101, 102 are closed.
The mobile unit 93 can thus be moved axially of the piping by repeating these operations. Furthermore, since the foregoing motions can be reversed, the mobile unit can be advanced in either direction along the pipes.
Though the sliding stroke is 10 mm in the test apparatus, the sliding stroke can be lengthened to make possible a longer range of movement covered by one operation.
Thus, after a worker mounts the mobile unit at an initially set position, the mobile unit is made to repeat the foregoing operations by remote control, thereby being made to walk across and slide along the pipes automatically while examining the pipes. Then, when the entire examination procedure ends, the mobile unit 93 is made to move in the opposite direction in order to return to the initially set position.
However, since the remotely controlled mobile unit 93 requires a travelling space around the pipes which includes the height of the unit itself, e.g. a space of about 500 mm in the case of outlet pipes 85, it is difficult to apply the unit to the narrow confines among the innermost outlet pipes 85 in the spaces surrounding the horizontal portions of the pipes.